The present invention relates to polycarbonate and a process for production thereof, and more particularly to novel polycarbonate which is excellent in all of flame retardance, impact resistance, fluidity and transparency and also to a process for efficiently producing said novel polycarbonate. 2. Description of Related Art
As flame retardant polycarbonates, a copolymer of tetrahalogenobisphenolsulfone and bisphenol A (BPA) (Japanese Patent Application Laid-Open No. 123294/1976), polycarbonate having an aromatic monosulfonyl group at the terminal thereof (Japanese Patent Application Laid-Open No. 21497/1979), a copolymer of tetrabromobisphenol A and BPA (Japanese Patent Application Laid-Open No. 155233/1982), polycarbonate having a sulfonic acid salt at the terminal thereof (PCT Japanese Patent Application Laid-Open No. 501212/1985), and so on have heretofore been known.
These conventional polycarbonates, however, are not sufficiently satisfactory in impact resistance, fluidity or transparency although they have high flame retardance. That is, polycarbonate excellent in all of flame retardance, impact resistance, fluidity and transparency has not yet been obtained.
Japanese Patent Publication No. 40715/1971 discloses polycarbonate produced using pentabromophenol as a molecular weight modifier. In the examples of the specification of Japanese Patent Publication No. 40715/1971, there are prepared only polycarbonates having a bromine content of 4.2% by weight or 3.3% by weight. Polycarbonate having such bromine contents, however, cannot be expected flame retardance of the extent that satisfies the standard V-0 specified in UL 94 1/16 inch (thickness). Furthermore, there is no description concerning impact resistance and fluidity of polycarbonate and, therefore, it can be seen that properties such as impact resistance and fluidity are not taken into consideration at all.
Japanese Patent Publication No. 41422/1972 discloses polycarbonate derived from tetrabromobispeenol A which is terminated in halogenated phenols. In this polycarbonate, however, neither impact resistance nor fluidity is taken into consideration and, therefore, it is considered that the polycarbonate is intended to be used merely as a flame retardant.